Thermal imaging members and methods

ABSTRACT

There are described thermal imaging members and thermal imaging methods utilizing unsymmetrical rhodamine compounds. The rhodamine color-forming compounds exhibit a first color when in a crystalline form and a second color, different from the first color, when in an amorphous form.

REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of priority of provisional patentapplication Ser. Nos. 60/680,088 and 60/680,212, both filed May 12,2005, the contents of which are incorporated herein by reference intheir entireties.

This application is related to the following commonly assigned, UnitedStates patent applications and patents, the contents of which areincorporated herein by reference in their entireties:

U.S. Pat. No. 6,801,233 B2;

U.S. Pat. No. 6,906,735 B2;

U.S. Pat. No. 6,951,952 B2;

U.S. Pat. No. 7,008,759 B2;

U.S. patent application Ser. No. 10/806,749, filed Mar. 23, 2004, whichis a division of U.S. Pat. No. 6,801,233 B2;

United States Patent Application Publication No. US2004/0176248 A1;(Attorney docket No. A-8544AFP);

United States Patent Application Publication No. US2004/0204317 A1;(Attorney Docket No. A-8586AFP);

United States Patent Application Publication No. US2004/0171817 A1;(Attorney Docket No. A-8589AFP);

U.S. patent application Ser. No. 11/400,735; filed on Apr. 6, 2006(Attorney Docket No. A-8598);

U.S. patent application Ser. No. 11/400,734; filed on Apr. 6, 2006(Attorney Docket No. A-8606); and

U.S. patent application Ser. No. ______; filed on even date herewith,Express Mail No.: EV 669114318 US (Attorney Docket No. A-8614).

FIELD OF THE INVENTION

This invention relates to thermal imaging members and methods and, moreparticularly, to such imaging members and methods in which there areutilized a color-former that exhibits one color in the crystalline formand a second, different color in the liquid, or amorphous, form.

BACKGROUND OF THE INVENTION

The development of thermal print heads (linear arrays ofindividually-addressable heating elements) has led to the development ofa wide variety of thermally-sensitive imaging materials. In some ofthese, known as “thermal transfer” systems, heat is used to move coloredmaterial from a donor sheet to a receiver sheet. Alternatively, heat maybe used to convert a colorless coating on a single sheet into a coloredimage, in a process known as “direct thermal” imaging. Direct thermalimaging has the advantage over thermal transfer of the simplicity of asingle sheet. On the other hand, unless a fixing step is incorporated,direct thermal systems are still sensitive to heat after thermalprinting. If a stable image is needed from an unfixed direct thermalsystem, the temperature for coloration must be higher than anytemperature that the image is likely to encounter during normal use. Aproblem arises in that the higher the temperature for coloration, theless sensitive the imaging member will be when printed with the thermalprint head. High sensitivity is important for maximum speed of printing,for maximizing the longevity of the print head, and for energyconservation in mobile, battery-powered printers. As described in moredetail below, maximizing sensitivity while maintaining stability is moreeasily achieved if the temperature of coloration of a direct thermalmedium is substantially independent of the heating time.

Thermal print heads address one line of the image at a time. Forreasonable printing times, each line of the image is heated for aboutten milliseconds or less. Storage of the medium (prior to printing or inthe form of the final image) may need to be for years, however. Thus,for high imaging sensitivity, a high degree of coloration is required ina short time of heating, while for good stability a low degree ofcoloration is required for a long time of heating.

Most chemical reactions speed up with increasing temperature. Therefore,the temperature required for coloration in the short heating timeavailable from a thermal print head will normally be higher than thetemperature needed to cause coloration during the long storage time.Reversing this order of temperatures would be a very difficult task, butmaintaining a substantially time-interval-independent temperature ofcoloration, such that the temperatures required for coloration over bothlong and short time intervals are substantially the same, is a goal thatis achieved by the present invention.

There are other reasons why a time-interval-independent colorationtemperature may be desirable. It may, for example, be required toperform a second thermal step, requiring a relatively long time ofheating, after printing. An example of such a step would be thermallamination of an image. The temperature of coloration of the imagingmaterial during the time required for thermal lamination must be higherthan the lamination temperature (otherwise the material would becomecolorized during lamination). It would be preferred that the imagingtemperature be higher than the lamination temperature by as small amargin as possible. This would be the case for time-interval-independenttemperature of coloration.

Finally, the imaging system may comprise more than one color-forminglayer and be designed to be printed with a single thermal print-head, asdescribed in the above-mentioned U.S. Pat. No. 6,801,233 B2. In oneembodiment of the imaging system, the topmost color-forming layer formscolor in a relatively short time at a relatively high temperature, whilethe lower layer or layers form color in a relatively long time at arelatively low temperature. An ideal topmost layer for this type ofdirect thermal imaging system would have time-interval-independenttemperature of coloration.

Prior art direct thermal imaging systems have used several differentchemical mechanisms to produce a change in color. Some have employedcompounds that are intrinsically unstable, and which decompose to form avisible color when heated. Such color changes may involve a unimolecularchemical reaction. This reaction may cause color to be formed from acolorless precursor, the color of a colored material to change, or acolored material to bleach. The rate of the reaction is accelerated byheat. For example, U.S. Pat. No. 3,488,705 discloses thermally unstableorganic acid salts of triarylmethane dyes that are decomposed andbleached upon heating. U.S. Pat. No. 3,745,009 reissued as U.S. ReissuePat. No. 29,168 and U.S. Pat. No. 3,832,212 disclose heat-sensitivecompounds for thermography containing a heterocyclic nitrogen atomsubstituted with an —OR group, for example, a carbonate group, thatdecolorize by undergoing homolytic or heterolytic cleavage of thenitrogen-oxygen bond upon heating to produce an RO+ ion or RO′ radicaland a dye base or dye radical which may in part fragment further. U.S.Pat. No. 4,380,629 discloses styryl-like compounds that undergocoloration or bleaching, reversibly or irreversibly, via ring-openingand ring-closing in response to activating energies. U.S. Pat. No.4,720,449 describes an intramolecular acylation reaction that converts acolorless molecule to a colored form. U.S. Pat. No. 4,243,052 describespyrolysis of a mixed carbonate of a quinophthalone precursor that may beused to form a dye. U.S. Pat. No. 4,602,263 describes athermally-removable protecting group that may be used to reveal a dye orto change the color of a dye. U.S. Pat. No. 5,350,870 describes anintramolecular acylation reaction that may be used to induce a colorchange. A further example of a unimolecular color-forming reaction isdescribed in “New Thermo-Response Dyes: Coloration by the ClaisenRearrangement and Intramolecular Acid-Base Reaction”, Masahiko Inouye,Kikuo Tsuchiya, and Teijiro Kitao, Angew. Chem. Int. Ed. Engl., 31, pp.204-5 (1992).

In all of the above-mentioned examples, control of the chemical reactionis achieved through the change in rate that occurs with changingtemperature. Thermally-induced changes in rates of chemical reactions inthe absence of phase changes may often be approximated by the Arrheniusequation, in which the rate constant increases exponentially as thereciprocal of absolute temperature decreases (i.e., as temperatureincreases). The slope of the straight line relating the logarithm of therate constant to the reciprocal of the absolute temperature isproportional to the so-called “activation energy”. The prior artcompounds described above are coated in an amorphous state prior toimaging, and thus no change in phase is expected or described asoccurring between room temperature and the imaging temperature. Thus, asemployed in the prior art, these compounds exhibit stronglytime-interval-dependent coloration temperatures. Some of these prior artcompounds are described as having been isolated in crystalline form.Nevertheless, in no case is there mentioned in this prior art any changein activation energy of the color-forming reaction that may occur whencrystals of the compounds are melted.

Other prior art thermal imaging media depend upon melting to triggerimage formation. Typically, two or more chemical compounds that reacttogether to produce a color change are coated onto a substrate in such away that they are segregated from one another, for example, asdispersions of small crystals. Melting, either of the compoundsthemselves or of an additional fusible vehicle, brings them into contactwith one another and causes a visible image to be formed. For example, acolorless dye precursor may form color upon heat-induced contact with areagent. This reagent may be a Bronsted acid, as described in “ImagingProcesses and Materials”, Neblette's Eighth Edition, J. Sturge, V.Walworth, A. Shepp, Eds., Van Nostrand Reinhold, 1989, pp. 274-275, or aLewis acid, as described for example in U.S. Pat. No. 4,636,819.Suitable dye precursors for use with acidic reagents are described, forexample, in U.S. Pat. No. 2,417,897, South African Patent 68-00170,South African Patent 68-00323 and Ger. Offenlegungschrift 2,259,409.Further examples of such dyes may be found in “Synthesis and Propertiesof Phthalide-type Color Formers”, by Ina Fletcher and Rudolf Zink, in“Chemistry and Applications of Leuco Dyes”, Muthyala Ed., Plenum Press,New York, 1997. The acidic material may for example be a phenolderivative or an aromatic carboxylic acid derivative. Such thermalimaging materials and various combinations thereof are now well known,and various methods of preparing heat-sensitive recording elementsemploying these materials also are well known and have been described,for example, in U.S. Pat. Nos. 3,539,375, 4,401,717 and 4,415,633.

Prior art systems in which at least two separate components are mixedfollowing a melting transition suffer from the drawback that thetemperature required to form an image in a very short time interval by athermal print-head may be substantially higher than the temperaturerequired to colorize the medium during longer periods of heating. Thisdifference is caused by the change in the rate of the diffusion neededto mix the molten components together, which may become limiting whenheat is applied for very short periods. The temperature may need to beraised well above the melting points of the individual components toovercome this slow rate of diffusion. Diffusion rates may not belimiting during long periods of heating, however, and the temperature atwhich coloration takes place in these cases may actually be less thanthe melting point of either individual component, occurring at theeutectic melting point of the mixture of crystalline materials.

U.S. patent application Ser. No. 10/789,648, filed Feb. 27, 2004 (UnitedStates Patent Application Publication No. US2004/0176248 A1), andassigned to the same assignee as the present application, is directed toa thermal imaging method wherein a dye is converted from one form inwhich the dye has one color to another form in which the dye has asecond color, e.g., from colorless to colored.

Japanese Published Application No. 9-241553 discloses inkjet recordinginks containing certain asymmetrical rhodamine dyes. U.S. Pat. No.4,390,616 discloses thermal imaging members and methods utilizingcertain rhodamine dyes.

As the state of the imaging art advances and efforts are made to providenew imaging systems that can meet new performance, requirements, itwould be advantageous to have thermal imaging systems which utilize yetanother class of dyes.

SUMMARY OF THE INVENTION

It is therefore an object of this invention to provide novel thermalimaging members and methods.

Another object of the invention is to provide such thermal imagingmembers and methods that utilize a color-former that exhibits differentcolors when in the crystalline form than when in the amorphous form.

Yet another object of the invention is to provide imaging members andmethods that utilize certain rhodamine color-formers.

According to one aspect of the invention there are provided novelthermal imaging members and methods that utilize certain rhodaminecolor-forming compounds that exhibit a first color when in a crystallineform and a second color, different from the first color, when in anamorphous form.

In one embodiment of the invention there are provided novel thermalimaging members and methods that utilize compounds that are representedby formula I

wherein:

R₁, R₃, R₄, R₅, R₆, R₇, R₈ and R₁₄ are each independently selected fromthe group consisting of hydrogen, substituted or unsubstituted alkyl,preferably having from 1 to 18 carbon atoms, alkenyl or substitutedalkenyl, preferably having from 1 to 18 carbon atoms, heterocycloalkyl,substituted heterocycloalkyl, alkoxy, substituted alkoxy, substitutedcarbonyl, acylamino, halogen, aryl, substituted aryl, heteroaryl andsubstituted heteroaryl;

R₂ is selected from the group consisting of hydrogen, alkyl orsubstituted alkyl, preferably having from 1 to 18 carbon atoms, alkenylor substituted alkenyl, preferably having from 1 to 18 carbon atoms,heterocycloalkyl and substituted heterocycloalkyl; or

R₂ and R₃ taken together with the nitrogen atom to which they areattached can form a substituted or unsubstituted saturated heterocyclicring system, such as, for example, substituted and unsubstitutedmorpholines, pyrrolidines, and piperidines;

R₉ is absent or selected from the group consisting of hydrogen,substituted or unsubstituted alkyl, preferably having from 1 to 18carbon atoms, substituted or unsubstituted alkenyl, preferably havingfrom 1 to 18 carbon atoms, heterocycloalkyl, substitutedheterocycloalkyl, alkoxy, substituted alkoxy, substituted carbonyl,halogen, aryl, substituted aryl, heteroaryl, substituted heteroaryl,amino, substituted amino, alkylamino, substituted alkylamino, arylaminoand substituted arylamino;

R₁₀, R₁₁ and R₁₂ are each independently selected from the groupconsisting of hydrogen, substituted or unsubstituted alkyl, preferablyhaving from 1 to 18 carbon atoms, substituted or unsubstituted alkenyl,preferably having from 1 to 18 carbon atoms, heterocycloalkyl,substituted heterocycloalkyl, alkoxy, substituted alkoxy, substitutedcarbonyl, halogen, aryl, substituted aryl, heteroaryl, substitutedheteroaryl, amino, substituted amino, alkylamino, substitutedalkylamino, arylamino and substituted arylamino;

R₁₃ is selected from the group consisting of hydrogen, substituted orunsubstituted alkyl, preferably having from 1 to 18 carbon atoms,substituted or unsubstituted alkenyl, preferably having from 1 to 18carbon atoms, heterocycloalkyl and substituted heterocycloalkyl;

R₁₄ is selected from the group consisting of hydrogen, substituted orunsubstituted alkyl, preferably having from 1 to 18 carbon atoms,substituted or unsubstituted alkenyl, preferably having from 1 to 18carbon atoms, heterocycloalkyl and substituted heterocycloalkyl; or

R₁₃ and R₁₄ taken together with the atoms to which they are attached canform a 5- or 6-membered heterocyclic ring such as, for example, indolineor tetrahydroquinoline;

R₁₅, R₁₆, R₁₇ and R₁₈ are each independently selected from the groupconsisting of hydrogen, substituted or unsubstituted alkyl, preferablyhaving from 1 to 18 carbon atoms, substituted or unsubstituted alkenyl,preferably having from 1 to 18 carbon atoms, heterocycloalkyl,substituted heterocycloalkyl, alkoxy, substituted alkoxy, substitutedcarbonyl, halogen, aryl, substituted aryl, heteroaryl, substitutedheteroaryl, amino, substituted amino, alkylamino, substitutedalkylamino, arylamino and substituted arylamino;

X₁ is carbon or nitrogen; and at least one of R₂ and R₁₃ is hydrogen.

The substituents are preferably chosen to minimize the water solubilityof the compounds and facilitate the formation of a colorless form innon-polar, non-protic solvents. In turn, the colorless lactone form ofthe compounds must be capable of melting to form the colored form.

A preferred group of compounds for use according to the invention arethose represented by formula I wherein R₂ and R₃ taken together form apyrrolidine ring, R₁₀, R₁₁ and R₁₃ each is hydrogen, X₁ is carbon andR₁, R₄, R₅, R₆, R₇, R₈, R₉, R₁₂, R₁₄, R₁₅, R₁₆, R₁₇ and R₁₈ are aspreviously described with respect to formula I.

A second preferred group of compounds for use according to the inventionare those represented by formula I wherein R₂ is hydrogen, R₃ is alkyl,R₁₀ and R₁₁ are each halogen, R₁₃ is alkyl, X₁ is carbon and R₁, R₄, R₅,R₆, R₇, R₈, R₉, R₁₂, R₁₄, R₁₅, R₁₆, R₁₇ and R₁₈ are as described withrespect to formula I.

A third preferred group of compounds for use according to the inventionare those represented by formula I wherein R₂ is hydrogen, R₃ is aryl orsubstituted aryl, R₁₃ and R₁₄ are alkyl and R₁, R₄, R₅, R₆, R₇, R₈, R₉,R₁₀, R₁₁, R₁₂, R₁₅, R₁₆, R₁₇, R₁₉ and X₁ are as described with respectto formula I.

Particularly preferred rhodamine compounds for use according to theinvention are those represented by formula I in which R₁, R₄, R₅, R₆,R₇, R₈, R₉ and R₁₂ are each hydrogen; R₂ is hydrogen or alkyl havingfrom 1-18 carbon atoms, R₃ is alkyl having from 1-18 carbon atoms, arylor substituted aryl, or R₂ and R₃ taken together with the nitrogen atomto which they are attached form a pyrrolidine ring; R₁₀ and R₁₁ are eachindependently hydrogen or halogen; R₁₃ is hydrogen or alkyl, preferablyhaving from 1-18 carbon atoms, R₁₄ is hydrogen or alkyl having from 1-18carbon atoms, X₁ is carbon and R₁₅, R₁₆, R₁₇ and R₁₈ are eachindependently hydrogen, alkyl having from 1-18 carbon atoms, or halogen.

The conversion from the crystalline form to the amorphous form inaccordance with the thermal imaging members and thermal imaging methodsof the invention is carried out by applying heat to the compounds. Inthe thermal imaging methods of the invention thermal energy may beapplied to the thermal imaging members by any of the techniques known inthermal imaging such as from a thermal print head, a laser, a heatedstylus, etc.

In another embodiment, one or more thermal solvents, which arecrystalline materials, can be incorporated in the thermal imagingmember. The crystalline thermal solvent(s), upon being heated, melt anddissolve or liquefy, and thereby convert, at least partially, thecrystalline color-forming material to the amorphous form to form theimage.

When converted to the colored form the compounds of formula I have theopen form illustrated by formula II (for the case where R₂ in formula Iis hydrogen)

or formula III (for the case where R₁₃ in formula I is hydrogen).

wherein R₁, R₃-R₁₈, and X₁ are as defined above with respect to formulaI.

According to the invention the compounds of formula I may beincorporated in any thermal imaging members and used in any thermalimaging methods including thermal transfer imaging members and methodsand direct thermal imaging members and methods. The thermal imagingmembers of the invention may be for use in thermal transfer imaging suchas is disclosed in U.S. Pat. No. 6,537,410 B2. Conventional methods forcolor thermal imaging such as thermal wax transfer printing anddye-diffusion thermal transfer typically involve the use of separatedonor and receiver materials. The donor material typically has a coloredimage-forming material, or a color-forming imaging material, coated on asurface of a substrate and the image-forming material or thecolor-forming imaging material is transferred thermally to the receivermaterial. In order to make multicolor images, a donor material withsuccessive patches of differently-colored, or different color-forming,material may be used. In the case of printers having eitherinterchangeable cassettes or more than one thermal head, differentmonochrome donor ribbons are utilized and multiple color separations aremade and deposited successively above one another.

The thermal imaging members according to the invention may be for use indirect thermal printing methods and such thermal imaging members includeall the color-forming reagents necessary to form an image in the member.Such direct thermal imaging members according to the invention may beused in any direct thermal imaging method such as, for example,disclosed in U.S. Pat. No. 6,801,233 B2.

Thermal imaging members according to the invention generally comprise asubstrate carrying at least one image-forming layer including a compoundaccording to formula I in the crystalline form, which can be converted,at least partially to an amorphous form, the amorphous form havingintrinsically a different color from the crystalline form. The imagingmember may be monochromatic, in which an image-forming layer includes atleast one compound of formula I, or polychromatic. Multicolor directthermal imaging members include at least two, and preferably three,image-forming layers and the temperature at which an image is formed inat least one of the image-forming layers is preferablytime-interval-independent. Preferred imaging members according to theinvention are direct multicolor thermal imaging members.

Any suitable thermal solvents may be incorporated in the thermal imagingmembers of the invention. Suitable thermal solvents include, forexample, alkanols containing at least about 12 carbon atoms, alkanediolscontaining at least about 12 carbon atoms, monocarboxylic acidscontaining at least about 12 carbon atoms, esters and amides of suchacids, aryl sulfonamides and hydroxyalkyl-substituted arenes.

Specific preferred thermal solvents include: tetradecan-1-ol,hexadecan-1-ol, octadecan-1-ol, dodecane-1,2-diol, hexadecane-1,16-diol,myristic acid, palmitic acid, stearic acid, methyl docosanoate,1,4-bis(hydroxymethyl)benzene, and p-toluenesulfonamide.

Particularly preferred thermal solvents are diaryl sulfones such asdiphenylsulfone, 4,4′-dimethyldiphenylsulfone, phenyl p-tolylsulfone and4,4′-dichlorodiphenylsulfone.

It is possible that the dissolution of the compounds of formula I by athermal solvent may lead to an amorphous form (in which the compound isdissolved in the amorphous thermal solvent) in which the proportion ofthe open, colored form is different from the proportion that would bepresent in the amorphous form resulting from melting the compound offormula I alone (i.e., without interaction with the thermal solvent). Inparticular, the proportion of the open, colored form of the compound inthe amorphous material may be enhanced by use of hydrogen-bonding oracidic thermal solvents. Materials that increase the proportion of thecolor-forming material that is in the open, colored form are hereinafterreferred to as “developers”. It is possible that the same compound mayserve the function of thermal solvent and developer. Preferreddevelopers include phenols such as2,2′-methylenebis(6-tert-butyl-4-methylphenol),2,2′-methylenebis(6-tert-Butyl-4-Ethyl-Phenol),2,2′-ethylidenebis(4,6-di-tert-butylphenol),bis[2-hydroxy-5-methyl-3-(1-methylcyclohexyl)phenyl]-methane,1,3,5-tris(2,6-dimethyl-3-hydroxy-4-tert-butylbenzyl) isocyanurate,2,6-bis[[3-(1,1-dimethylethyl)-2-hydroxy-5-methylphenyl]methyl]-4-methyl-phenol,2,2′-butylidenebis[6-(1,1-dimethylethyl)-4-methyl-phenol,2,2′-(3,5,5-trimethylhexylidene)bis[4,6-dimethyl-phenol],2,2′-methylenebis[4,6-bis(1,1-dimethylethyl)-phenol,2,2′-(2-methylpropylidene)bis[4,6-dimethyl-phenol],1,1,3-tris(2-methyl-4-hydroxy-5-t-butylphenyl)butane,tris(3,5-di-t-butyl-4-hydroxybenzyl)isocyanurate,2,2′-thiobis(4-tert-octylphenol), and3-tert-butyl-4-hydroxy-5-methylphenyl sulfide.

In order for the image formed by the amorphous color-former to be stableagainst recrystallization back to the crystalline form, preferably theglass transition temperature (T_(g)) of the amorphous mixture of thecolor-former and any thermal solvent should be higher than anytemperature that the final image must survive. Typically, it ispreferred that the T_(g) of the amorphous, colored material be at leastabout 50° C., and ideally above about 60° C. In order to ensure that theT_(g) is sufficiently high for a stable image to be formed, materialshaving a high T_(g) may be added to the color-forming composition. Suchmaterials, hereinafter referred to as “stabilizers”, when dissolved inthe amorphous mixture of color-former, optional thermal solvent, andoptional developer, serve to increase the thermal stability of theimage.

Preferred stabilizers have a T₉ that is at least about 60° C., andpreferably above about 80° C. Examples of such stabilizers are theaforementioned 1,3,5-tris(2,6-dimethyl-3-hydroxy-4-tert-butylbenzyl)isocyanurate (T_(g) 123° C.) and1,1,3-tris(2-methyl-4-hydroxy-5-t-butylphenyl)butane (T_(g) 101° C.). Itwill be clear that the stabilizer molecule may also serve as a thermalsolvent or as a developer.

For example, the color-forming material may itself have a meltingtemperature above the desired temperature for imaging, and a T_(g) (inthe amorphous form) of about 60° C. In order to produce a color-formingcomposition melting at the desired temperature, it may be combined witha thermal solvent (for example, a diaryl sulfone) that melts at thedesired temperature for imaging. The combination of thermal solvent andcolor-forming material may, however, have a T_(g) that is substantiallylower than 60° C., rendering the (amorphous) image unstable. In thiscase, a stabilizer such as1,3,5-tris(2,6-dimethyl-3-hydroxy-4-tert-butylbenzyl) isocyanurate maybe added, to raise the T_(g) of the amorphous material. In addition,there may be provided a developer, for example, a phenolic compound suchas 2,2′-ethylidenebis(4,6-di-tert-butylphenol), in order to increase theproportion of the color-forming material that is in the colored form inthe amorphous phase.

Preferably the color-forming compound of the present invention, the(optional) thermal solvent, the (optional) developer and the (optional)stabilizer are each predominantly in their crystalline forms prior toimaging. By “predominantly” is meant at least about 50%. During imaging,at least one of these materials melts and an amorphous mixture of thematerials is formed. The amorphous mixture is colored, whereas thecrystalline starting materials are not.

It is possible that one of the components in the amorphous, coloredmixture may recrystallize after the image has been formed. It isdesirable that such recrystallization not change the color of the image.In the case that a color-former, thermal solvent, developer andstabilizer are used, the thermal solvent may typically recrystallizewithout greatly affecting the color of the image.

Preferred thermal imaging members according to the invention are directthermal imaging members, particularly those having the structuresdescribed in commonly assigned U.S. Pat. No. 6,801,233 B2.

Other preferred thermal imaging members are those for use in thermaltransfer imaging methods, particularly those having the structuresdescribed in commonly assigned U.S. Pat. No. 6,537,410.

Further preferred thermal imaging members are thermal transfer imagingmembers having the structures described in commonly assigned U.S. Pat.No. 6,054,246.

DETAILED DESCRIPTION OF THE INVENTION

Compounds in the crystalline state commonly have properties, includingcolor, that are very different from those of the same compounds in anamorphous form. In a crystal, a molecule is typically held in a singleconformation (or, more rarely, in a small number of conformations) bythe packing forces of the lattice. Likewise, if a molecule can exist inmore than one interconverting isomeric form, only one of such isomericforms is commonly present in the crystalline state. In amorphous form orsolution, on the other hand, the compound may explore its wholeconformational and isomeric space, and only a small proportion of thepopulation of individual molecules of the compound may at any one timeexhibit the particular conformation or isomeric form adopted in thecrystal. Compounds of the present invention exhibit tautomerism in whichat least one tautomeric form is colorless, and at least anothertautomeric form is colored. The crystalline form of compounds of thepresent invention comprises predominantly the colorless tautomer.

In a first embodiment of the invention there are provided thermalimaging members and methods which utilize a compound whose colorlesstautomer is represented by formula I as described above.

Specific representative compounds utilized according to the inventionare those of formula I which are shown in Table I in which thesubstituents R₁, R₄, R₅, R₆, R₇, R₈, R₉, R₁₁, R₁₅, R₁₇, R₁₈ are allhydrogen, X₁ is carbon and R₂, R₃, R₁₀, R₁₁, R₁₃, R₁₄ and R₁₆ are asshown:

TABLE I DYE R₂ R₃ R₁₀ R₁₁ R₁₃ R₁₄ R₁₆ M.P. λmax I n-C10H21 H H H—(CH₂)₃— H 124 570 II 2-EtPh H H H  C8H17 C2H5 H 144 548 III Ph H H HC4H9 H H 172 552 IV 2-MePh H H H  C8H17 CH3 H 152 548 V 2-MePh H H H C6H13 CH3 H 199 548 VI 2-MePh H H H C4H9 H H 184 550 VII Cyclohexyl H HH C2H5 H H 212 544 VIII Adamantyl H H H C2H5 H H 240 544 IX Cyclohexyl HCl Cl C4H9 H H 193 554 X Adamantyl H Cl Cl C4H9 H H 252 554 XICyclohexyl H Cl Cl  C8H17 H H 162 554 XII —(CH₂)₄— H H H CH3 H 268 556XIII —(CH₂)₄— H H H CH3 4-F 272 552 XIV —(CH₂)₃CHCH₃— H H H CH3 4-F 228552

Compounds I and VII-XIV are novel compounds which are disclosed andclaimed in co-pending U.S. patent application Ser. No. ______, (AttorneyDocket No. A-8614) filed on even date herewith, Express Mail No.: EV669114318 US.

DEFINITIONS

The term “alkyl” as used herein refers to saturated straight-chain,branched-chain or cyclic hydrocarbon radicals. Examples of alkylradicals include, but are not limited to, methyl, ethyl, propyl,isopropyl, n-butyl, tert-butyl, neopentyl, n-hexyl, cyclohexyl, n-octyl,n-decyl, n-dodecyl and n-hexadecyl radicals.

The term “alkenyl” as used herein refers to unsaturated straight-chain,branched-chain or cyclic hydrocarbon radicals. Examples of alkenylradicals include, but are not limited to, allyl, butenyl, hexenyl andcyclohexenyl radicals.

The term “alkynyl” as used herein refers to unsaturated hydrocarbonradicals having at least one carbon-carbon triple bond. Representativealkynyl groups include, but are not limited to, ethynyl, 1-propynyl,1-butynyl, isopentynyl, 1,3-hexadiynyl, n-hexynyl, 3-pentynyl,1-hexen-3-ynyl and the like.

The terms “halo” and “halogen,” as used herein, refer to an atomselected from fluorine, chlorine, bromine and iodine.

The term “aryl,” as used herein, refers to a mono-, bicyclic ortricyclic carbocyclic ring system having one, two or three aromaticrings including, but not limited to, phenyl, naphthyl, anthryl, azulyl,tetrahydronaphthyl, indanyl, indenyl and the like.

The term “heteroaryl,” as used herein, refers to a cyclic aromaticradical having from five to ten ring atoms of which one ring atom isselected from S, O and N; zero, one or two ring atoms are additionalheteroatoms independently selected from S, O and N; and the remainingring atoms are carbon, the radical being joined to the rest of themolecule via any of the ring atoms, such as, for example, pyridinyl,pyrazinyl, pyrimidinyl, pyrrolyl, pyrazolyl, imidazolyl, thiazolyl,oxazolyl, isooxazolyl, thiadiazolyl, oxadiazolyl, thiophenyl, furanyl,quinolinyl, isoquinolinyl, and the like.

The term “heterocycloalkyl,” as used herein, refers to a non-aromatic3-, 4-, 5-, 6- or 7-membered ring or a bi- or tri-cyclic groupcomprising fused six-membered rings having between one and threeheteroatoms independently selected from oxygen, sulfur and nitrogen,wherein (i) each 5-membered ring has 0 to 1 double bonds and each6-membered ring has 0 to 2 double bonds, (ii) the nitrogen and sulfurheteroatoms may optionally be oxidized, (iii) the nitrogen heteroatommay optionally be quaternized, and (iv) any of the above heterocyclicrings may be fused to a benzene ring. Representative heterocyclesinclude, but are not limited to, pyrrolidinyl, pyrazolinyl,pyrazolidinyl, imidazolinyl, imidazolidinyl, piperidinyl, piperazinyl,oxazolidinyl, isoxazolidinyl, morpholinyl, thiazolidinyl,isothiazolidinyl, and tetrahydrofuryl.

The term “carbonyl” as used herein refers to a carbonyl group, attachedto the parent molecular moiety through the carbon atom, this carbon atomalso bearing a hydrogen atom, or in the case of a “substituted carbonyl”a substituent as described in the definition of “substituted” below.

The term “acyl” as used herein refers to groups containing a carbonylmoiety. Examples of acyl radicals include, but are not limited to,formyl, acetyl, propionyl, benzoyl and naphthoyl.

The term “alkoxy”, as used herein, refers to a substituted orunsubstituted alkyl, alkenyl or heterocycloalkyl group, as previouslydefined, attached to the parent molecular moiety through an oxygen atom.Examples of alkoxy radicals include, but are not limited to, methoxy,ethoxy, propoxy, isopropoxy, n-butoxy, tert-butoxy, neopentyloxy andn-hexyloxy.

The term “aryloxy” as used herein refers to a substituted orunsubstituted aryl or heteroaryl group, as previously defined, attachedto the parent molecular moiety through an oxygen atom. Examples ofaryloxy include, but are not limited to, phenoxy, p-methylphenoxy,naphthoxy and the like.

The term “alkylamino”, as used herein, refers to a substituted orunsubstituted alkyl, alkenyl or heterocycloalkyl group, as previouslydefined, attached to the parent molecular moiety through a nitrogenatom. Examples of alkylamino radicals include, but are not limited to,methylamino, ethylamino, hexylamino and dodecylamino.

The term “arylamino”, as used herein, refers to a substituted orunsubstituted aryl or heteroaryl group, as previously defined, attachedto the parent molecular moiety through a nitrogen atom.

The term “substituted” as used herein in phrases such as “substitutedalkyl”, “substituted alkenyl”, “substituted aryl”, “substitutedheteroaryl”, “substituted heterocycloalkyl”, “substituted carbonyl”,“substituted alkoxy”, “substituted acyl”, “substituted amino”,“substituted aryloxy”, and the like, refers to independent replacementof one or more of the hydrogen atoms on the substituted moiety withsubstituents independently selected from, but not limited to, alkyl,alkenyl, heterocycloalkyl, alkoxy, aryloxy, hydroxy, amino, alkylamino,arylamino, cyano, halo, mercapto, nitro, carbonyl, acyl, aryl andheteroaryl groups.

The term “substituted” as used herein in phrases such as “substitutednitrogen”, “substituted oxygen” and “substituted sulfur” refers tonitrogen, oxygen or sulfur substituted with alkyl, aryl, or heteroarylgroups. Examples include, but are not limited to, alkyl and aryl etherssuch as methoxy, ethoxy or phenoxy; alkyl or aryl thioethers such asthiomethoxy, thioethoxy and thiophenyl; alkyl or aryl amines such asdimethylamino, diethylamino, diphenylamino, phenylamino, andN-methyl-N-phenylamino.

According to the invention, there are utilized molecules exhibitingtautomerism in which at least one tautomeric form is colorless, and atleast another tautomeric form is colored. Crystallization of theequilibrating mixture of the two tautomeric forms is carried out so asto produce colorless crystals. The solvent chosen to perform thecrystallization will typically be one of such polarity (and otherchemical properties, such as hydrogen-bonding ability) that the purecolorless crystal form is favored, either in the equilibrium between thecolorless and colored forms in solution, or in having lower solubilityin the solvent than the colored form. The choice of solvent is usuallydetermined empirically for a particular mixture of tautomers.

Upon conversion of the pure crystalline colorless form to an amorphousform, the equilibrium between the two tautomers is re-established. Theproportion of the amorphous material that is colored (i.e., theproportion that is in the colored tautomeric form) may vary, but ispreferably at least about 10%.

The colored and colorless tautomeric forms of the molecules utilizedaccording to the present invention should meet certain criteria forimage quality and permanence. The colorless form, which is preferablythe crystalline form, should have minimal visible absorption. It shouldbe stable to light, heating below the melting point, humidity, and otherenvironmental factors such as ozone, oxygen, nitrogen oxides,fingerprint oils, etc. These environmental factors are well known tothose skilled in the imaging art. The colored, amorphous form should bestable also to the above mentioned conditions, and in addition shouldnot recrystallize to the colorless form under normal handling conditionsof the image. The colored form should have a spectral absorptionappropriate for digital color rendition. Typically, the colored formshould be yellow (blue-absorbing), magenta (green-absorbing), cyan (redabsorbing), or black, without undue absorption in an unintended spectralregion. For non-photographic applications, however, it may be requiredthat the colored form not be one of the subtractive primary colors, butrather a particular spot color (for example, orange, blue, etc.).

The compounds used according to the invention may be prepared bysynthetic processes which are known to those skilled in the art,particularly in view of the state of the art in organic syntheticprocesses, and the present disclosure and specific preparatory examplesprovided below herein.

Generally, symmetrical rhodamine dyes can be prepared in one step from3′,6′-dichlorofluorans by reacting two equivalents of an aromatic oraliphatic amine as described in U.S. Pat. No. 4,602,263, GB2311075 andDE81056. The unsymmetrical rhodamine dyes are then prepared by theselective monoalkylation of symmetrical rhodamines using sodium hydridein dimethyl sulfoxide as described in U.S. Pat. Nos. 4,602,263 and4,826,976.

Alternatively, the unsymmetrical rhodamines can be prepared by use of analternate synthetic pathway in which one equivalent of an N-alkylanilineis reacted selectively with the 3′,6′-dichlorofluoran using aluminumchloride as a catalyst to produce 3′-chloro-6′-N-alkyl-N-arylfluorans.These products are isolated and purified prior to reacting with a secondequivalent of an aromatic or aliphatic amine. Zinc chloride is used asthe catalyst for the second addition. DE139727 describes the selectiveaddition of anilines to 3′,6′-dichlorofluorans to produce3′-chloro-6′-arylaminofluorans using a mixture of zinc chloride and zincoxide at 160° C.

Unsymmetrical rhodamines can also be made from 2-benzoyl benzoic acidderivatives by condensation with 3-arylamino phenols or 3-alkylaminophenols as described in Chemistry and Applications of Leuco Dyes, pp.180-191 R. Muthyala, Ed., Plenum Press, New York and London, 1997 andalso U.S. Pat. Nos. 4,390,616 and 4,436,920.

To optimize the chromophore, melting point, degree of coloration, lightstability and solubility of the dyes of this application a variety ofanilines, N-alkylanilines, aliphatic amines and dichlorofluorans areutilized.

The 3′,6′-dichlorofluorans are synthesized from the correspondingfluoresceins using thionyl chloride and dimethylformamide in a variationof the method of Hurd described in the Journal of the Amer. ChemicalSoc. 59, 112 (1937).

Careful recrystallization from solvent mixtures such as hexanes/acetoneor hexanes/ethyl acetate produces colorless crystalline material whichis preferred for use in thermal imaging members.

As described above, the thermal imaging members of the invention can bedirect thermal imaging members wherein an image is formed in the memberitself or they can be thermal transfer imaging members wherebyimage-forming material is transferred to an image-receiving member. Themelting point of the molecules used in direct thermal imaging members ofthe present invention is preferably in the range of about 60° C. toabout 300° C. Melting points lower than about 60° C. lead to directthermal imaging members that are unstable to temperatures occasionallyencountered during handling of the members before or after imaging,while melting temperatures above about 300° C. render the compoundsdifficult to colorize to a full density with a conventional thermalprint head. It should be noted, however, that there are uses for certaincompounds that do not require the use of thermal print heads (forexample, laser imaging).

To form a preferred direct thermal imaging system, the crystalline,colorless form of the compounds is made into a dispersion in a solventin which the compound is insoluble or only sparingly soluble, by any ofthe methods known in the art for forming dispersions. Such methodsinclude grinding, attriting, etc. The particular solvent chosen willdepend upon the particular crystalline material. Solvents that may beused include water, organic solvents such as hydrocarbons, esters,alcohols, ketones, nitriles, and organic halide solvents such aschlorinated and fluorinated hydrocarbons. The dispersed crystallinematerial may be combined with a binder, which may be polymeric. Suitablebinders include water-soluble polymers such as poly(vinyl alcohol),poly(vinylpyrrolidinone) and cellulose derivatives, water-dispersedlatices such as styrene/butadiene or poly(urethane) derivatives, oralternatively hydrocarbon-soluble polymers such as polyethylene,polypropylene, copolymers of ethylene and norbornene, and polystyrene.This list is not intended to be exhaustive, but is merely intended toindicate the breadth of choice available for the polymeric binder. Thebinder may be dissolved or dispersed in the solvent.

Following preparation of the dispersion of the compound of the presentinvention, and optional addition of a polymeric binder, the resultantfluid is coated onto a substrate using any of the techniques well-knownin the coating art. These include slot, gravure, Mayer rod, roll,cascade, spray, and curtain coating techniques. The image-forming layerso formed is optionally overcoated with a protective layer or layers.

Where materials of the present invention are used to prepare an imagingmember of the type described in U.S. Pat. No. 6,801,233 B2 the processdescribed above is followed for each of the imaging layers. Successivelayers may be coated sequentially, in tandem, or in a combination ofsequential and tandem coatings.

A particularly preferred thermal imaging member according to the presentinvention is constructed as follows.

The substrate is a filled, white poly(ethylene terephthalate) base ofthickness about 75 microns, Melinex 339, available from Dupont TeijinFilms, Hopewell, Va.

A first layer deposited on the substrate is an optional oxygen barrierlayer composed of a fully hydrolyzed poly(vinyl alcohol), for example,Celvol 325, available from Celanese, Dallas, Tex. (96.7% by weight),glyoxal (a crosslinker, 3% by weight) and Zonyl FSN (a coating aid,available from Dupont, Wilmington, Del., 0.3% by weight). This layer,when present, has a coverage of about 1.0 g/m².

Deposited either directly onto the substrate, or onto the optionaloxygen barrier layer, is a cyan image-forming layer composed of a cyancolor-former having melting point 210° C., of the type disclosed in theaforementioned U.S. Pat. No. 7,008,759 (1 part by weight), diphenylsulfone (a thermal solvent having melting point 125° C., coated as anaqueous dispersion of crystals having average particle size under 1micron, 3.4 parts by weight), Lowinox WSP (a phenolic antioxidant,available from Great Lakes Chemical Co., West Lafayette, Ind., coated asan aqueous dispersion of crystals having average particle size under 1micron, 0.75 parts by weight), Chinox 1790 (a second phenolicantioxidant, available from Chitec Chemical, Taiwan, coated as anaqueous dispersion of crystals having average particle size under 1micron, 1 part by weight), poly(vinyl alcohol) (a binder, Celvol 205,available from Celanese, Dallas, Tex., 2.7 parts by weight), glyoxal(0.084 parts by weight) and Zonyl FSN (0.048 parts by weight). Thislayer has a coverage of about 2.5 g/m².

Deposited onto the cyan color-forming layer is a barrier layer thatcontains a fluorescent brightener. This layer is composed of a fullyhydrolyzed poly(vinyl alcohol), for example, the abovementioned Celvol325, available from Celanese, Dallas, Tex. (3.75 parts by weight),glyoxal (0.08 parts by weight), Leucophor BCF P115 (a fluorescentbrightener, available from Clariant Corp., Charlotte, N.C., 0.5 parts byweight), boric acid (0.38 parts by weight) and Zonyl FSN (0.05 parts byweight). This layer has a coverage of about 1.5 g/m².

Deposited on the barrier layer is a thermally-insulating interlayercomposed of Glascol C-44 (a latex available from Ciba SpecialtyChemicals Corporation, Tarrytown, N.Y., 18 parts by weight), Joncryl1601 (a latex available from Johnson Polymer, Sturtevant, Wis., 12 partsby weight) and Zonyl FSN (0.02 parts by weight). This layer has acoverage of about 13 g/m².

Deposited on the thermally-insulating interlayer is a barrier layercomposed of a fully hydrolyzed poly(vinyl alcohol), for example, theabovementioned Celvol 325, available from Celanese, Dallas, Tex. (2.47parts by weight), glyoxal (0.07 parts by weight), boric acid (0.25 partsby weight) and Zonyl FSN (0.06 parts by weight). This layer has acoverage of about 1.0 g/m².

Deposited on the barrier layer is a magenta color-forming layer,composed of a magenta color-former of the present invention, preferablyDye IV, having a melting point of 152° C.; a phenolic antioxidant (Anox29, having melting point 161-164° C., available from Great LakesChemical Co., West Lafayette, Ind., coated as an aqueous dispersion ofcrystals having average particle size under 1 micron, 3.58 parts byweight), Lowinox CA22 (a second phenolic antioxidant, available fromGreat Lakes Chemical Co., West Lafayette, Ind., coated as an aqueousdispersion of crystals having average particle size under 1 micron, 0.72parts by weight), poly(vinyl alcohol) (a binder, Celvol 205, availablefrom Celanese, Dallas, Tex., 2 parts by weight), the potassium salt ofCarboset 325 (an acrylic copolymer, available from Noveon, Cleveland,Ohio, 1 part by weight) glyoxal (0.06 parts by weight) and Zonyl FSN(0.06 parts by weight). This layer has a coverage of about 2.7 g/m².

Deposited on the magenta color-forming layer is a barrier layer composedof a fully hydrolyzed poly(vinyl alcohol), for example, theabove-mentioned Celvol 325, available from Celanese, Dallas, Tex. (2.47parts by weight), glyoxal (0.07 parts by weight), boric acid (0.25 partsby weight) and Zonyl FSN (0.06 parts by weight). This layer has acoverage of about 1.0 g/m².

Deposited on the barrier layer is a second thermally-insulatinginterlayer composed of Glascol C-44 (1 part by weight), Joncryl 1601 (alatex available from Johnson Polymer, 0.67 parts by weight) and ZonylFSN (0.004 parts by weight). This layer has a coverage of about 2.5g/m².

Deposited on the second interlayer is a barrier layer composed of afully hydrolyzed poly(vinyl alcohol), for example, the abovementionedCelvol 325, available from Celanese, Dallas, Tex. (1 part by weight),glyoxal (0.03 parts by weight), boric acid (0.1 parts by weight) andZonyl FSN (0.037 parts by weight). This layer has a coverage of about0.5 g/m².

Deposited on the barrier layer is a yellow color-forming layer composedof Dye XI (having melting point 202-203° C.) described in U.S. patentapplication Ser. No. 10/789,566, filed Feb. 27, 2004, United StatesPatent Application Publication No. US2004/0204317 A1 (4.57 parts byweight), poly(vinyl alcohol) (a binder, Celvol 540, available fromCelanese, Dallas, Tex., 1.98 parts by weight), a colloidal silica(Snowtex 0-40, available from Nissan Chemical Industries, Ltd Tokyo,Japan, 0.1 parts by weight), glyoxal (0.06 parts by weight) and ZonylFSN (0.017 parts by weight). This layer has a coverage of about 1.6g/m².

Deposited on the yellow color-forming layer is a barrier layer composedof a fully hydrolyzed poly(vinyl alcohol), for example, theabove-mentioned Celvol 325, available from Celanese, Dallas, Tex. (1part by weight), glyoxal (0.03 parts by weight), boric acid (0.1 partsby weight) and Zonyl FSN (0.037 parts by weight). This layer has acoverage of about 0.5 g/m².

Deposited on the barrier layer is an ultra-violet blocking layercomposed of a nanoparticulate grade of titanium dioxide (MS-7, availablefrom Kobo Products Inc., South Plainfield, N.J., 1 part by weight),poly(vinyl alcohol) (a binder, Elvanol 40-16, available from DuPont,Wilmington, Del., 0.4 parts by weight), Curesan 199 (a crosslinker,available from BASF Corp., Appleton, Wis., 0.16 parts by weight) andZonyl FSN (0.027 parts by weight). This layer has a coverage of about1.56 g/m².

Deposited on the ultra-violet blocking layer is an overcoat composed ofa latex (XK-101, available from NeoResins, Inc., Wilmington, Mass., 1part by weight), a styrene/maleic acid copolymer (SMA 17352H, availablefrom Sartomer Company, Wilmington, Pa., 0.17 parts by weight), acrosslinker (Bayhydur VPLS 2336, available from BayerMaterialScience,Pittsburgh, Pa., 1 part by weight), zinc stearate (Hidorin F-115P,available from Cytech Products Inc., Elizabethtown, Ky., 0.66 parts byweight) and Zonyl FSN (0.04 parts by weight). This layer has a coverageof about 0.75 g/m².

Optimal conditions for printing a yellow image using the preferredthermal imaging member described above are as follows.

Thermal printing head parameters:

Pixels per inch: 300

Resistor size: 2×(31.5×120) microns (split resistor)

Resistance: 3000 Ohm

Glaze Thickness: 110 microns

Pressure: 3 lb/linear inch

Dot pattern: Slanted grid.

The yellow color-forming layer is printed as shown in the table below.The line cycle time is divided into individual pulses of 75% duty cycle.The thermal imaging member is preheated by contact with the thermalprinting head glaze at the heat sink temperature over a distance ofabout 0.3 mm.

Yellow printing Heat sink 25° C. temperature Dpi 300 (transportdirection) Voltage 38 Line speed 6 inch/sec Pulse 12.5 microsec interval# pulses used 8-17

Optimal conditions for printing a magenta image using the preferredthermal imaging member described above are as follows. Thermal printinghead parameters:

Pixels per inch: 300

Resistor size: 2×(31.5×120) microns (split resistor)

Resistance: 3000 Ohm

Glaze Thickness: 200 microns

Pressure: 3 lb/linear inch

Dot pattern: Slanted grid.

The magenta color-forming layer is printed as shown in the table below.The line cycle time is divided into individual pulses of 7.14% dutycycle. The thermal imaging member is preheated by contact with thethermal printing head glaze at the heat sink temperature over a distanceof about 0.3 mm.

Magenta printing Heat sink 30° C. temperature Dpi 300 (transportdirection) Voltage 38 Line speed 0.75 inch/sec Pulse 131 microsecinterval # pulses used 20-30

Optimal conditions for printing a cyan image using the preferred thermalimaging member described above are as follows. Thermal printing headparameters:

Pixels per inch: 300

Resistor size: 2×(31.5×180) microns

(split resistor)

Resistance: 3000 Ohm

Glaze Thickness: 200 microns

Pressure: 3 lb/linear inch

Dot pattern: Slanted grid.

The cyan color-forming layer is printed as shown in the table below. Theline cycle time is divided into individual pulses of about 4.5% dutycycle. The thermal imaging member is preheated by contact with thethermal printing head glaze at the heat sink temperature over a distanceof about 0.3 mm.

Cyan printing Heat sink 50° C. temperature Dpi 300 (transport direction)Voltage 38 Line speed 0.2 inch/sec Pulse 280 microsec interval # pulsesused 33-42

EXAMPLES

The invention will now be described further in detail with respect tospecific embodiments by way of examples, it being understood that theseare intended to be illustrative only and the invention is not limited tothe materials, amounts, procedures and process parameters, etc. recitedtherein. All parts and percentages recited are by weight unlessotherwise specified.

Example I Synthesis of N-acetyl-N-octylaniline

1-Octylbromide (39 mL, 224 mmol, 1.12 eq) was added dropwise to amixture of acetanilide (27 g, 200 mmol, 1 eq) in dimethylsulfoxide (130mL), containing potassium hydroxide pellets (18.87 g, 300 mmol, 1.5 eq),at room temperature. After all the octyl bromide was added the reactionmixture was heated to 50-55° C. for 1.5 hours. The reaction mixture wascooled and poured into water (1 L), stirred for 45 minutes and extractedwith hexanes (3×400 mL). The hexane extracts were combined, dried oversodium sulfate and evaporated to give 48.4 g (196 mmol, 98%) ofcolorless oil. The product was identified by NMR spectroscopy and massspectrometry and was used without further purification.

Synthesis of N-octylaniline

To N-acetyl-N-octylaniline (48.4 g, 196 mmol) there was added 4Nhydrochloric acid (100 mL) and the mixture heated to 100-110° C. andstirred at this temperature for 4 days. The reaction mixture was cooledto ambient temperature, diluted with water (100 mL), and hexanes (200mL). The pH of the reaction mixture was brought to pH 14 by addition of45% potassium hydroxide with cooling by an ice bath. The layers wereseparated and the aqueous layer washed with hexanes (100 mL). Thecombined organic layers were dried over sodium sulfate and concentratedby rotary evaporation to give the desired product as a light brown oil(40 g, 195 mmol, 99%). The product was identified by NMR spectroscopyand mass spectrometry and in general was used without furtherpurification. Analytically pure product was obtained by distillation atreduced pressure: by 145-150° C. (0.5 mm).

Synthesis of 5,6-dichlorofluorescein

To a 5 L 3-neck flask fitted with a mechanical stirrer and a thermometerwas added 4,5-dichlorophthalic acid (502 g, 2.13 mol) andmethanesulfonic acid (2 L). The mixture was stirred at 90° C. for onehour. The mixture was cooled to 80° C. and resorcinol (470 g, 4.27 mol)was added all at once. The dark mixture was heated at 105° C. for onehour. The warm mixture was poured into a stirred mixture of ice (6 kg)and water (5 L). The mixture was stirred for 30 minutes and filtered.The filter cake was washed with water (3×500 mL). The wet filter cakewas stirred with propyl acetate (2 L) and filtered again. The wet cakewas dried to a constant weight and placed in the original reactionvessel. Propyl acetate (2 L) was added and the stirred mixture washeated to 90° C. and allowed to cool to room temperature and filtered.The filter cake was washed with acetone (0.4 L) and hexane (0.4 L). Themustard yellow solid was dried to a constant weight in the vacuum ovento afford 930 g (109% yield). The product was identified by NMRspectroscopy and mass spectrometry.

Synthesis of 3′,6′,5,6-tetrachlorofluoran

To a 5 L 3-necked fitted with a mechanical stirrer, a thermometer, and adropping funnel was added dichlorofluorescein (930 g, ca. 2.13 mol),sulfolane (2.4 L), and dimethylformamide (152 mL, 1.9 moles). Thestirred mixture was warmed to 90° C. and phosphorus oxychloride (0.72 L)was added dropwise over one hour while keeping the temperature between90 and 95° C. After the addition was complete, the mixture was kept atthe same temperature for one hour and poured into acetone:water (2:1, 11L). The mixture was stirred for one hour and filtered. The filter cakewas washed with acetone: water (2 L) and dried in a vacuum oven to aconstant weight. A beige solid was obtained. (805 g, 1.84 mol, 86%overall yield for two steps). The product was identified by NMRspectroscopy and mass spectrometry.

Synthesis of 3′-chloro-6′-tetrahydroquinolinofluoran

A mixture of dichlorofluoran (3.7 g, 0.01 mol), aluminum chloride (9 g,0.07 mol) and tetrahydroquinoline (2.6 g, 0.02 moles) in sulfolane (25ml) was held at 150° C. for 18 hours. The reaction mixture was quenchedinto 100 ml of water. The solid was filtered off, washed with water anddried. The product was purified on silica gel using 2% methanol inmethylene chloride to yield 3′-chloro-6′-tetrahydroquinolinofluoran (250mg, 0.54 mmol, 5.4%). The product was identified by NMR spectroscopy andmass spectrometry.

Synthesis of 3′-chloro-6′-(N-ethylaniline)-5,6-dichlorofluoran

A three-necked flask equipped with mechanic stirrer and thermometer wascharged with 3′,6′,5,6-tetrachlorofluoran (8.8 g, 20 mmol) and 40 mL ofsulfolane. Aluminum chloride (11.0 g, 80 mmol) was added to the mixturein portions with stirring. At 60° C., N-ethylaniline (6.05 g, 50 mmol,2.5 eq) was added dropwise over 15 minutes. The reaction was monitoredby HPLC. After the starting materials were consumed, the reactionmixture was cooled and poured into 2 N HCl (500 mL). The precipitatedsolid was filtered, washed and air-dried. The free base was obtained bydissolving the salt in DMF, followed by pouring into ammonia hydroxidesolution. The product was washed with water and dried. (Yield: 9.36 g,17 mmol, 85%) The product was identified by NMR spectroscopy and massspectrometry.

Synthesis of 3′-N-butylanilino-6′-chlorofluoran

3′,6′-dichlorofluoran (15.0 g, 40.6 mmol) was taken up in sulfolane (80mL), heated to 60° C. and aluminum chloride (21.0 g, 157.9 mmol, 3.9eq.) was added in one portion. N-Butylaniline (15 mL, 98.3 mmol, 2.4eq.) was then added dropwise over 5 minutes and the reaction was heatedat 80° C. for 1 hour. The reaction mixture was poured into 3Nhydrochloric acid and ice. The resulting precipitate was filtered,washed with water and dried overnight to afford the crude3′-N-butylanilino-6′-chlorofluoran (18.9 g, 39.2 mmol, 96%) which wasused as such. The product was identified by NMR spectroscopy and massspectrometry.

Synthesis of 3′-chloro-6′-(N-octylaniline)-5,6-dichlorofluoran

To a solution of 3′,6′,5,6-tetrachlorofluorescein (8.8 g, 0.02 mol) insulfolane (40 mL) was added aluminum chloride (11:0 g, 0.08 mol) inportions with stirring. This was followed by the addition ofN-octylaniline (4.4 g, 0.022 mol) at 50° C. over 5 minutes. After 30minutes, triethylamine (6.0 g, 0.06 mol) was added dropwise over 10minutes. After the starting materials were consumed (HPLC) the reactionmixture was cooled and poured into 2 N HCl (500 mL). The precipitatedsolid was filtered, washed and air-dried. The free base product wasobtained by dissolving the salt in DMF, followed by pouring intoammonium hydroxide solution. The product was identified by NMRspectroscopy and mass spectrometry.

Synthesis of 3′-chloro-6′-(2-methylanilino)-fluoran

To a suspension of 3′,6′-dichlorofluoran (30 g, 81 mmol) in sulfolane(120 mL) was added AlCl₃ (3.0 eq., 244 mmol, 32.4 g) and the mixture waswarmed to 60° C. Toluidine (1.1 eq., 89.4 mmol 9.6 g) was added and thetemperature of the orange solution was maintained at 60° C. for 10minutes. Neat triethylamine (1.05 eq., 85.4 mmol, 8.64 g was addeddropwise with stirring over a period of 10 minutes. After stirring at70° C. open to air for 4 hours, the solution was poured into avigorously stirred beaker of water (1 L). The resulting suspension wasfiltered, and the collected solids were dissolved in ethyl acetate (500mL). The organic extracts were dried over sodium sulfate and adsorbed onsilica (˜100 g). The product was purified by silica gel columnchromatography (1:1 Hexane/EtOAc) to yield an orange solid. The productwas identified by NMR spectroscopy and mass spectrometry.

Example II Synthesis of Dye I

A mixture of 3′-chloro-6′-tetrahydroquinolinofluoran (100 mg, 0.2 mmol),decylamine (100 mg, 0.6 mmol), and zinc chloride (100 mg, 0.7 mmol) insulfolane (3 mL) was held at 150° C. for 3 hours. The reaction mixturewas quenched into 10 ml of water. The solid was filtered off, washedwith water and dried. The product was purified by silica gelchromatography using 2% methanol in methylene chloride to yield3′N-decylamino-6-tetrahydroquinoline fluoran as an off-white solid (42mg, 0.07 mmol, 35%). The product was identified by NMR spectroscopy andmass spectrometry.

Example III Synthesis of Dye VII

To a solution of 3′-N-ethylanilino-6′-chlorofluoran (1.82 g, 4 mmol) in12 ml of sulfolane was added zinc chloride (1.63 g, 12 mmol), zinc oxide(0.32, 4 mmol) and cyclohexylamine (1.6 g, 16 mmol). The reactionmixture was heated to 140° C. under stirring overnight (18 hours). Afterbeing cooled to room temperature, the reaction mixture was poured intowater (100 mL) and the precipitated crude product was obtained byfiltration, dried in air and dissolved in methylene chloride (50 mL).After removing insoluble solids by filtration, the resulting filtratewas subjected to chromatography (silica gel, hexane/ethyl acetate aseluent). The isolated oil product was recrystallized in a mixed solutionof hexane and ethyl acetate to give 0.7 g of light pink crystals, m.p.:212-214° C.). The product was identified by NMR spectroscopy and massspectrometry.

Example IV Synthesis of Dye VIII

To a solution of 3′-N-ethylanilino-6′-chlorofluoran (1.82 g, 4 mmol) in12 ml of sulfolane was added zinc chloride (1.63 g, 12 mmol), zinc oxide(0.32, 4 mmol) and adamantylamine (2.4 g, 16 mmol). The reaction mixturewas heated to 150° C. under stirring overnight. After being cooled toroom temperature, the reaction mixture was poured into 100 ml water, theprecipitated crude product obtained by filtration and dried in vacuumand then dissolved in methylene chloride. After removal of insolublesolid, the resulting filtrate was concentrated to the appropriate volumefor being loaded on chromatography (silica gel, hexane/ethyl acetate aseluent). The isolated oil was converted into light pink crystals in amixed solution of hexane and ethyl acetate under stirring (0.55 g, m.p.:240-242° C.). The product was identified by NMR spectroscopy and massspectrometry.

Example V Synthesis of Dye IX

To a solution of 3′-chloro-6′-(N-butylaniline)-5,6-dichlorofluoran (2.2g, 4 mmol) in 12 ml of sulfolane was added zinc chloride (1.63 g, 12mmol), zinc oxide (0.32, 4 mmol) and cyclohexylamine (1.6 g, 16 mmol).The reaction mixture was heated to 140° C. under stirring overnight.After being cooled to room temperature, the reaction mixture was pouredinto water (100 mL) and the precipitated crude product was obtained byfiltration, subjected to chromatography (silica gel, hexane/ethylacetate as eluent) using methylene chloride as solvent for loading. Theisolated oil product was recrystallized in hexane mixed with 30% ofethyl acetate to give 0.56 g of light pink crystals, m.p.: 193-195° C.The product was identified by NMR spectroscopy and mass spectrometry.

Example VI Synthesis of Dye X

To a solution of 3′-chloro-6′-(N-butylaniline)-5,6-dichlorofluoran (2.2g, 4 mmol) in 12 ml of sulfolane was added zinc chloride (1.63 g, 12mmol), zinc oxide (0.32, 4 mmol) and adamantylamine (2.4 g, 16 mmol).The reaction mixture was heated to 150° C. under stirring overnight.After being cooled to room temperature, the reaction mixture was pouredinto water (100 mL) and the precipitated crude product obtained byfiltration, dried in vacuum and directly subjected to chromatography(silica gel, hexane/ethyl acetate as eluent) with methylene chloride asloading solvent, ignoring insoluble solid. The isolated oil product wastransformed into light pink crystals by recrystallization from a mixedsolution of hexane and ethyl acetate (0.45 g, m.p.: 252-254° C.). Theproduct was identified by NMR spectroscopy and mass spectrometry.

Example VII Synthesis of Dye XI

To a solution of 3′-chloro-6′-(N-octylaniline)-5,6-dichlorofluoran (1.82g, 3 mmol) in 12 ml of sulfolane was added zinc chloride (1.30 g, 9mmol), zinc oxide (0.25 g, 3 mmol) and cyclohexylamine (1.2 g, 12 mmol).The reaction mixture was heated to 140° C. under stirring overnight.After being cooled to room temperature, the reaction mixture was pouredinto 2 N HCl (100 mL), the precipitated crude product obtained byfiltration, dried in vacuum and dissolved in DMF (20 mL). The mixed DMFsolution was poured into 10% ammonium hydroxide (100 mL). The resultingred crude product was subjected to chromatography (silica gel,hexane/ethyl acetate as eluent) for further purification. The isolatedoil product was converted into light pink crystals by recrystallizationfrom a mixed solution of hexane and ethyl acetate (0.77 g, m.p.:162-164° C.). The product was identified by NMR spectroscopy and massspectrometry.

Example VIII Synthesis of Dye XII

To a solution of 3′-chloro-6′-(2-methylanilino)-fluoran (3 g, 7 mmol) insulfolane (10 mL) was added lutidine (1.1 eq., 7.7 mmol, 0.83 g)followed by ZnO (0.8 eq., 5.6 mmol, 456 mg) and ZnCl₂ (3.0 eq., 21 mmol,2.86 g). The solution was warmed to 100° C. and pyrrolidine (1.5 eq.,10.5 mmol, 747 mg) was added. After 1 hour the red solution was pouredinto water (500 mL), filtered and the collected solids were dissolved inethyl acetate (500 mL). The organic extracts were washed with 0.5 N KOH(100 mL) and dried with magnesium sulfate. The solvent was removed underreduced pressure and the product purified by silica gel columnchromatography (1:1 Hexanes/EtOAc→EtOAc gradient) to yield ID747 (2.49g, 5.25 mmol, 75%). The purified product was crystallized fromacetone/hexanes to yield 1.5 g of pink powder. The product wasidentified by NMR spectroscopy and mass spectrometry.

Example IX Synthesis of Dye XIII

To a suspension of 3′,6′-dichlorofluoran (184.5 gm; 0.5 mol) insulfolane (800 mL) was added AlCl₃ (3.0 eq., 200 g; 1.5 mol) and themixture was warmed to 60° C. followed by the addition of.4-fluoro-2-methylaniline (68.8 gm; 0.55 mol). The temperature of theorange solution was maintained at 80° C. for 10 minutes. Neattriethylamine (1.21 eq., 82.5 mL; 0.605 mol) was added drop wise withstirring over a period of 10 minutes. After stirring at 80° C. for fourhours the completion of the reaction was followed by TLC of an aliquot(Ethyl acetate:hexanes, 1:4).

Lutidine (2.2 eq., 127.9 ml; 1.1 mol) and pyrrolidine (39.10 g; 0.55mol) were added to the warm reaction solution. The reaction mixture wasstirred at 80° C. overnight. The reaction did not go to completion basedon TLC even when extra lutidine and pyrrolidine were added. The reactionmixture was cooled and then poured into ice/water (1.0 L) and stirredfor 30 minutes and filtered. The filtrate was washed with of water (1.0L).

The resulting paste was dissolved in dichloromethane (2.0 L) and washedwith water. The organic layer was separated, dried over sodium sulfateand evaporated. The crude dye was purified by silica gel chromatographythrough a short plug. A gradient of ethyl acetate/hexane was used aseluent. The fractions containing pure product were combined, evaporatedand recrystallized from acetone to give colorless crystals of Dye XIII(83 g; 33.7%). DSC=283 C. The product was identified by NMR spectroscopyand mass spectrometry.

Example X Synthesis of Dye XIV

To a suspension of 3′,6′-dichlorofluoran (9.225 g, 25 mmol) in sulfolane(50 mL) was added AlCl₃ (3.0 eq., 10 g; 75 mmol) and the mixture waswarmed to 60° C. followed by the addition of 4-fluoro-toluidine (3.44 g;27.25 mmol). The temperature of the orange solution was maintained at80° C. for 10 minutes. Neat triethylamine (1.1 eq., 3.75 ml.; 27.25mmol) was added dropwise with stirring over a period of 10 minutes. Thereaction was stirred at 80° C. for 4 hours. The completion of thereaction was followed by TLC of an aliquot. (Ethyl acetate:hexane::1:4).

Lutidine (2.0 eq., 7.85 ml; 50 mmol) and 2-methyl-pyrrolidine (2.32 g;27.25 mmol) were added to the warm reaction solution. The reactionmixture was stirred at 80° C. overnight. The reaction did not go tocompletion based on TLC even when extra lutidine and pyrrolidine wereadded. The reaction mixture was cooled and then poured into ice/water(500 ml), stirred for 30 min., filtered and washed with water (100 mL).

The resulting paste was dissolved in 400 ml of dichloromethane andwashed with water. The organic layer was separated, dried over sodiumsulfate and evaporated. The crude dye was purified by silica gelchromatography. A gradient of ethyl acetate/hexane was used as eluent.The fractions containing pure product were combined, evaporated andrecrystallized from a mixture of acetone/hexanes to give colorlesscrystals of Dye XIV (4.12 g; 32.54%). The product was identified by NMRspectroscopy and mass spectrometry.

Example XI

This example illustrates a thermal imaging method according to theinvention.

The following materials were used in this example:

Celvol 205, a grade of poly(vinyl alcohol) available from CelaneseCorporation, Dallas, Tex.;

Celvol 325, a grade of poly(vinyl alcohol) available from CelaneseCorporation, Dallas, Tex.;

Celvol 540, a grade of poly(vinyl alcohol) available from CelaneseCorporation, Dallas, Tex.;

Elvanol 40-16, a grade of poly(vinyl alcohol) available from DuPontCompany Americas, Wilmington, Del.;

Neocryl XK-101, available from DSM NeoResins, Wilmington, Mass.;

NeoCryl A-639, available from DSM NeoResins, Wilmington, Mass.;

Ucar 451, a styrene-acrylic latex available from Dow Chemical, Cary,N.C.;

Bayhydur VP LS2336, available from Bayer Material Science LLC,Pittsburgh, Pa.;

Glascol C44, a polyacrylamide available from Ciba Specialty Chemicals,Tarrytown, N.J.;

Joncryl J1601, a styrene-acrylic emulsion from Johnson Polymer,Sturtevant, Wis.:

Leucophor BCF P115 (a fluorescent brightener, available from ClariantCorp., Charlotte, N.C.);

Titanium dioxide, MS-7, available from Kobo Products Inc., SouthPlainfield, N.J.;

Titanium dioxide white pigment Ti-Pure® R900, available from DuPont,Wilmington, Del.;

Zonyl FSN, a surfactant, available from DuPont Corporation, Wilmington,Del.;

Diphenylsulfone available from Seal Sands Chemical, Seal Sands, UK;

2,2′-Methylenebis(6-tert-butyl-4-methylphenol) available from GreatLakes Chemical, West Lafayette, Ind.;

2,2′-Methylenebis(6-tert-Butyl-4-Ethyl-Phenol) available from GreatLakes Chemical, West Lafayette, Ind.;

2,2′-Ethylidenebis(4,6-di-tert-butylphenol) Available from Great LakesChemical, West Lafayette, Ind.;

Bis[2-hydroxy-5-methyl-3-(1-methylcyclohexyl)phenyl]-methane availablefrom Great Lakes Chemical, West Lafayette, Ind.;

1,3,5-Tris(2,6-dimethyl-3-hydroxy-4-tert-butylbenzyl) isocyanurateavailable from Great Lakes Chemical, West Lafayette, Ind.;

Pluronic 25R4, a surfactant available from BASF, Florham Park, N.J.;

Surfynol CT-111, Surfynol CT-131 and Surfynol GA, surfactants availablefrom Air Products and Chemicals, Inc. Allentown, Pa.;

Tamol 731, a surfactant available from Rohm and Haas Co. Philadelphia,Pa.;

Triton X-100, a surfactant available from The Dow Chemical Company,Midland, Mich.;

Hidorin F-115P, a grade of zinc stearate available from Cytech ProductsInc., Elizabethtown, Ky.;

Nalco 30V-25, a silica dispersion available from ONDEO Nalco Company,Chicago, Ill.;

Snowtex a colloidal silica available from Nissan Chemical-AmericaCorporation, Houston, Tex.;

Melinex X967, a transparent poly(ethylene terephthalate) film base ofapproximately 5 mils in thickness, available from DuPont Teijin Films,Hopewell, Va.

Yellow Color Former: Dye VI described in U.S. patent application Ser.No. 10/789,566, filed Feb. 27, 2004, United States Patent ApplicationPublication No. US2004/0204317 A1;

Magenta Color Former: Dye IV of the present application;

Cyan Color Former: A dye,3′-(2,3-dihydro-1H-indol-1-yl)-4,5,6,7-tetrafluoro-6′-[(4-methoxy-2-methylphenyl)amino]-Spiro[isobenzofuran-1(3H),9′-[9H]xanthen]-3-one, made according to the procedures described inUnited States Patent Application Publication No. US2004/0191668.

The imaging member was prepared by successive coatings applied to asubstrate, Melinex X967, as follows:

A cyan image-forming layer was applied as follows:

Cyan Color Former (77.68 g, melting point 205 C) was dispersed in amixture of Pluronic 25R4 (2.06 g), Surfynol CT-131 (1.59 g of a 52%aqueous solution), Triton X100 (2.06 g) methyl acetate (48.16 g) andwater (143.4 g), using an attritor equipped with glass beads, stirredfor 18 hours at room temperature. The dispersion was then diluted withwater (275 g) so that the total solid content of the resultingdispersion was 15%.

Thermal solvent dispersion A: diphenylsulfone (212.72 g) was dispersedin a mixture comprising Tamol 731 (198 g of a 6.30% solution in water,adjusted with sulfuric acid to a pH of 5), Celvol 205 (125.5 g of a 20%solution in water) and water (213.8 g), using an attritor equipped withglass beads, and stirred for 18 hours at room temperature. The resultingdispersion was then diluted with water (500 g) so that the total solidcontent was 20%.

Thermal Solvent Dispersion B:Bis[2-hydroxy-5-methyl-3-(1-methylcyclohexyl)phenyl]-methane (360 g) wasdispersed in a mixture comprising Surfynol CT-151 (22.5 g of a 40%solution in water), Surfynol GA (25.7 g of a 70% solution in water) andwater (1392 g), using an attritor equipped with glass beads, stirred for18 hours at room temperature. The total solid content of the resultingdispersion was 20%.

Thermal Solvent Dispersion C:1,3,5-Tris(2,6-dimethyl-3-hydroxy-4-tert-butylbenzyl) isocyanurate(518.6 g) was dispersed in a mixture comprising sodium laurel sulfate(16.2 g), Surfynol CT-111 (5.1 g) and water (1260 g), using an attritorequipped with glass beads, and stirred for 18 hours at room temperature.The total solid content of the resulting dispersion was 30%.

The above dispersions were combined with water and the materials listedin the table below to make the coating fluid for the cyan dye-forminglayer in the proportions stated. The coating composition thus preparedwas coated onto Melinex X967 to give a layer with a dried thickness of 2microns.

% solids in Ingredient coating fluid Cyan Dye Dispersion 0.740 ThermalSolvent Dispersion A 2.58 Thermal Solvent Dispersion B 0.55 ThermalSolvent Dispersion C 0.740 Celvol 205 3.14 Zonyl FSN 0.020 Glyoxal 0.090

A barrier layer was next applied as follows:

A fluid was prepared from the materials listed in the table below bymixing in water and coated on top of the cyan dye-forming layer to adried thickness of 2 microns.

% solids in Ingredient coating fluid Celvol 125 3.75 Boric Acid 0.375Leucophor 115 0.500 Glyoxal 0.037 Zonyl FSN 0.047

An interlayer was next applied as follows:

Water was combined with the materials listed in the table below toprovide a coating fluid, which was coated onto the barrier layer for adried thickness of 13.5 microns.

% solids in Ingredient coating fluid Joncryl 1601 12.0 Glascol C44 18.0Zonyl FSN 0.020

A yellow image-forming layer was applied as follows:

Yellow Color Former (114 g) was dispersed in a mixture comprising Tamol681 (173.4 g of a 3.46% solution in water), methyl acetate (56 g) andwater (56.6 g), using an attritor equipped with glass beads, stirred for18 hours at room temperature. The total solid content of the resultingdispersion was 30%.

The above dispersion was combined with water and the materials listed inthe table below to make the coating fluid for the yellow dye-forminglayer in proportions stated. The coating composition thus prepared wascoated onto the interlayer prepared above for a dried thickness of 2microns.

% solids in Ingredients coating fluid Yellow dye dispersion 3.50 Celvol540 1.50 Snowtex 0-40 0.075 Zonyl FSN 0.050 Glyoxal 0.045

A second barrier layer was applied as follows:

Water was combined with the materials listed in the table below toprovide a coating fluid, which was coated onto the yellow color-forminglayer to give a dried thickness of 1.5 microns.

% solids in Ingredients coating fluid Celvol 325 3.25 Zonyl FSN 0.046Boric Acid 0.325

Next a UV absorbing layer was applied as follows:

Titanium dioxide (MS-7, 600 g) was dispersed in a mixture of styrenemaleic anhydride (264.7 g of a 34% aqueous solution), Zonyl FSN (1.20 g)and water (634.1 g) using a Meyers Mill for 18 hours followed by 12cycles through a Dyno-Mill. The resulting dispersion was then dilutedwith water (200 g) to give a dispersion with total solids of 40.7%.

Water was combined with the materials listed in the table below toprovide a coating fluid, which was coated onto the barrier layer aboveto give a dried thickness of 1.8 microns.

% solids in Ingredients coating fluid Elvanol 4016 2.69 Zonyl FSN 0.090Titanium Dioxide Dispersion 6.23%

An overcoat was applied as follows:

Water was combined with the materials listed in the table below toprovide a coating fluid, which was in-line blended with Bayhydur VP LS2336 (50% solution in methyl acetate) coated onto the UV absorbing layerfor a dried thickness of 1.5 microns.

% solids in Ingredients coating fluid XK 101 1.188 UCAR 451 1.859 ZonylFSN 0.097 Hidorin F-115P 0.699 Nalco 2327 1.747 Bayhydur VP LS 23361.410

On the opposite side of the Melinex base a magenta color-forming layerwas applied:

Magenta Color Former IV (79.9 g) was dispersed in a mixture comprisingSurfynol CT-111 (2.76 g of a 52% solution in water), Surfynol CT-131(3.64 g), methyl acetate (68 g) and water (270.7 g), using an attritorequipped with glass beads, stirred for 18 hours at room temperature. Thetotal solid content of the resulting dispersion was 20%.

The above dispersion was combined with water and the materials listed inthe table below to make the coating fluid for the magenta dye-forminglayer in the proportions stated. The coating composition thus preparedwas coated onto the Melinex X967 for a dried thickness of 2 microns.

% solids in Ingredients coating fluid Magenta Dye Dispersion 0.850Celvol 205 4.532 Nalco 2327 2.266 Thermal Solvent Dispersion A 5.10Thermal Solvent Dispersion B 0.640 Thermal Solvent Dispersion C 0.090Zonyl FSN 0.020 Glyoxal 0.110

Next a barrier layer was applied:

A fluid was prepared from the materials listed in the table below bymixing in water and coated on top of the cyan dye-forming layer to adried thickness of 2 microns.

% solids in Ingredient coating fluid Celvol 325 3.25 Boric Acid 0.325Zonyl FSN 0.046

Next a white reflecting layer was applied:

Titanium dioxide (TiPure® R-900, 272.3 kg) was dispersed in a mixture ofstyrene maleic anhydride 1440H (42.1 kg of a 34% aqueous solution),BYK-012 (0.268 kg) and water (68.3 kg) using a Meyers Mill for 18 hoursfollowed by 4 cycles through a Dyno-Mill. This process provided adispersion of 74.9% total solids.

The above dispersion was combined with water and the ingredients shownin the table below to give a coating fluid of 39.4% total solids. Thiscoating fluid was in-line blended with Bayhydur VP LS 2336 (50% solutionin methyl acetate) and coated onto the barrier layer for a driedthickness of 20 microns.

% solids in Ingredient coating fluid Celvol 205 0.848 Titanium DioxideDispersion 31.29 Neocryl XK-101 7.212 Zonyl FSN .042

For the final coating a backcoat was applied:

Water was combined with the materials listed in the table below toprovide a coating fluid, which was in-line blended with Bayhydur VP LS2336 (50% solution in methyl acetate) coated onto the UV absorbing layerfor a dried thickness of 1.5 microns.

% solids in Ingredients coating fluid XK 101 0.487 UCAR 451 2.557 ZonylFSN 0.097 Hidorin F-115P 0.690 Nalco 2327 1.747 Bayhydur VP LS 23361.420

The resulting imaging member was printed using a laboratory test-bedprinter equipped with two thermal heads, model KPT-163-12PAN20 (KyoceraCorporation, 6 Takedatobadono-cho, Fushimi-ku, Kyoto, Japan).

The following printing parameters were used:

Printhead width: 6.0 inch

Pixels per inch: 300

Resistor size: 70×120 microns

Resistance: 2800-3200 Ohm

Pressure: 1.5-2 lb/linear inch

Dot pattern: Rectangular grid.

The yellow layer was printed from the front side with a high power/shorttime condition. A lower power/longer time condition was used to printthe cyan layer which was also addressed from the front side. Theprinthead pulsing producing yellow coloration and the printhead pulsingproducing cyan coloration were interleaved, and were supplied by asingle print head in a single pass, so that a single print head wasprinting two colors synchronously.

The magenta layer was printed with a low-power, long-time condition fromthe backside (the side of the film base bearing the opaque TiO2 layer).

In addition to printing gradations of color for each of the three dyelayers, gradations of combined pairs of the colors and of thecombinations of all three colors, were printed. Table II summarizes theprinting results for this imaging example.

TABLE II Dmin Dmax Yellow 0.122 1.15 Magenta 0.149 1.43 Cyan 0.159 1.29Black 1.70

Although the invention has been described in detail with respect tovarious preferred embodiments, it is not intended to be limited thereto,but rather those skilled in the art will recognize that variations andmodifications are possible which are within the spirit of the inventionand the scope of the appended claims.

1. A thermal imaging member comprising a substrate carrying animage-forming layer comprising a compound represented by the formula

wherein: R₁, R₄, R₅, R₆, R₇, and R₈ are each independently selected fromthe group consisting of hydrogen, alkyl, substituted alkyl, alkenyl,substituted alkenyl, heterocycloalkyl, substituted heterocycloalkylalkoxy, substituted alkoxy, substituted carbonyl, acylamino, halogen,aryl, substituted aryl, heteroaryl and substituted heteroaryl; R₂ is a2-alkylphenyl group; R₃ is hydrogen; R₉ is absent or selected from thegroup consisting of hydrogen, alkyl, substituted alkyl, alkenyl,substituted alkenyl, heterocycloalkyl, substituted heterocycloalkyl,alkoxy, substituted alkoxy, substituted carbonyl, halogen, aryl,substituted aryl, heteroaryl, substituted heteroaryl, amino, substitutedamino, alkylamino, substituted alkylamino, arylamino and substitutedarylamino; R₁₀, R₁₁ and R₁₂ are each independently selected from thegroup consisting of hydrogen, alkyl, substituted alkyl, alkenyl,substituted alkenyl, heterocycloalkyl, substituted heterocycloalkyl,alkoxy, substituted alkoxy, substituted carbonyl, halogen, aryl,substituted aryl, heteroaryl, substituted heteroaryl, amino, substitutedamino, alkylamino, substituted alkylamino, arylamino and substitutedarylamino; R₁₃ is selected from the group consisting of alkyl,substituted alkyl, alkenyl, substituted alkenyl, heterocycloalkyl andsubstituted heterocycloalkyl; R₁₄ is selected from the group consistingof alkyl, substituted alkyl, alkenyl, substituted alkenyl,heterocycloalkyl and substituted heterocycloalkyl; R₁₅, R₁₆, R₁₇ and R₁₈are each independently selected from the group consisting of hydrogen,alkyl, substituted alkyl, alkenyl, substituted alkenyl,heterocycloalkyl, substituted heterocycloalkyl, alkoxy, substitutedalkoxy, substituted carbonyl, halogen, aryl, substituted aryl,heteroaryl, substituted heteroaryl, amino, substituted amino,alkylamino, substituted alkylamino, arylamino and substituted arylamino;and X₁ is carbon or nitrogen; wherein said compound is colorless in thecrystalline form and magenta colored in the amorphous form. 2-8.(canceled)